Analysis of triple-band binary metamaterial absorber based on low-permittivity all-dielectric resonance surface

Different from the conventional metamaterial absorbers(MAs),which used metal resonance surface and ternary structure(metal–dielectric-backplane),as an alternative route,the all-dielectric resonance surface(ADRS)made of single low-permittivity dielectric is proposed to design binary(dielectric backplane)metamaterial absorber(BMA).As an illustration,a triple-band BMA composed of ADRS with a metallic backplane is designed and fabricated,where the ADRS incorporates two dielectric layers with different hole-array structures.The absorbing mechanisms of this kind of absorber are analyzed via analyzing configurations of power loss density,electric field and magnetic field,as well as investigating dependences of absorbing properties on structure dimensions.The study indicates that the structural design of ADRS leads to reverse magnetic field rings distributed inside the dielectric,forming the strong couplings at the resonance frequencies.The proposed BMA relies on low-permittivity ADRS,with the rapid preparation and low cost greatly simplifying the design of MAs.The current concept is also suitable to design multi-band and broadband MAs worked at other bands,by changing the structural design of ADRS.

A novel high breakdown voltage and high switching speed GaN HEMT with p-GaN gate and hybrid AlGaN buffer layer for power electronics applications

A novel p-GaN gate GaN high-electron-mobility transistor(HEMT)with an AlGaN buffer layer and hybrid dielectric zone(H-HEMT)is proposed.The hybrid dielectric zone is located in the buffer and composed of horizontal arranged HfO2 zone and SiNx zone.The proposed H-HEMT is numerically simulated and optimized by the Silvaco TCAD tools(ATLAS),and the DC,breakdown,C-V and switching properties of the proposed device are characterized.The breakdown voltage of the proposed HEMT is significantly improved with the introduction of the hybrid dielectric zone,which can effectively modulate the electric field distribution in the GaN channel and the buffer.High breakdown voltage of 1490 V,low specific on-state resistance of 0.45 mΩ·cm2 and high Baliga's figure of merit(FOM)of 5.3 GW/cm2,small R onQ oss of 212 mΩ·nC,high turn-on speed 627 V/ns and high turn-off speed 87 V/ns are obtained at the same time with the gate-to-drain distance L gd of 6μm.

Lightweight porous silica foams with extreme-low dielectric permittivity and loss for future 6G wireless communication technologies

In the next generation wireless communication systems operating at near terahertz frequencies, dielectric substrates with the lowest possible permittivity and loss factor are becoming essential. In this work, highly porous (98.9% ± 0.1%) and lightweight silica foams (0.025 ± 0.005 g/cm3), that have extremely low relative permittivity (εr = 1.018 ± 0.003 at 300 GHz) and corresponding loss factor (tan δ< 3 × 10−4 at 300 GHz) are synthetized by a template-assisted sol-gel method. After dip-coating the slabs of foams with a thin film of cellulose nanofibers, sufficiently smooth surfaces are obtained, on which it is convenient to deposit electrically conductive planar thin films of metals important for applications in electronics and telecommunication devices. Here, micropatterns of Ag thin films are sputtered on the substrates through a shadow mask to demonstrate double split-ring resonator metamaterial structures as radio frequency filters operating in the sub-THz band.